DC relay

ABSTRACT

A direct current relay includes a plurality of contact pairs, and a plurality of magnets ( 5 ). Each of the plurality of contact pairs is configured having contacts ( 21, 22, 31 ) with contact regions ( 21   a,    22   a,    31   a ) disposed to allow opening and closure with respect to each other. The plurality of contact pairs are disposed such that the plurality of magnets ( 5 ) are disposed on one straight line, and the contact pairs are located between the magnets ( 5 ) on a line identical to the straight line. Each of the plurality of magnets ( 5 ) is provided to distort an arc generated between contacts ( 21, 22, 23, 31 ) on an occasion of relay cut off in a direction crossing the straight line. Even if a backward current flows, arcs will not interfere with each other, allowing extinguishing in a short time. Accordingly, a direct current relay can be obtained, capable of cutting off a high direct current voltage in a short time even on an occasion of backward current while minimizing the number of magnets and allowing down-sizing with a simple structure.

TECHNICAL FIELD

The present invention relates to a direct current relay. Particularly,the present invention relates to a direct current relay that canreliably cut off direct current by inhibiting interference between arcsgenerated at a plurality of pairs of contacts, when provided.

BACKGROUND ART

Recently, vehicles of high voltage (approximately 300V) such as hybridvehicles and fuel-cell powered vehicles have been developed from thestandpoint of environmental issues. Such vehicles include a controlcircuit constituted of a main battery of high direct current voltage anda high voltage circuit. In the case of an accident or the like, thebattery must be disconnected from the control circuit since itcorresponds to a high direct current voltage. To this end, a directcurrent relay formed of a mechanical contact is provided between thebattery and the control circuit.

In such relays, the cut off speed is extremely low since the arcgenerated when the high direct current voltage is to be cut off is verylarge. It was extremely difficult to achieve cut off in a short time. Inview of the foregoing, there is known a conventional structure ofplacing a magnet at the arc generating region to extend the arc byLorentz force (for example, refer to Japanese Patent No. 3321963).

The direct current relay disclosed in Japanese Patent No. 3321963includes two pairs of contacts, each contact pair being sandwiched by apair of magnets arranged so as to be orthogonal to a line connecting thecontact pairs. In this relay, the magnets forming a pair are arranged sothat the opposite magnetic pole facing each other differ. These pairs ofcontacts have the contacts provided so that current flows in series whenconnected.

In accordance with Japanese Patent No. 3321963, the arc generatedbetween the contacts, when each contact pair attains a non-contactstate, is distorted to extend on the line connecting the two contactpairs and towards the side opposite to the adjacent contact pair (outerside).

The conventional relay disclosed in Japanese Patent No. 3321963 requiresspace to ensure sufficient arc extension for immediate relay cutoffsince a pair of magnets are disposed corresponding to each contact pair,and the arc is extended outward of these contact pairs on a lineconnecting the two contact pairs through the action of the magneticfield.

The number of magnets is increased in order to dispose a pair of magnetsfor each contact pair having the attraction corresponding to the degreeof arc extension. This poses the problem that the entire relay isincreased in size.

Furthermore, the cost of the relay will become higher since theincreased number of pairs of magnets, one pair disposed for each contactpair, will induce further time and effort in the assembly procedure.

Hybrid vehicles and the like employ a system to convert kinetic energyinto electric energy to charge the battery at the time of deceleration.Therefore, a backward current (regenerative current) may be generated inthe relay. The need arises for a relay to be cut off even in the casewhere a backward current flows excessively.

However, if the relay is cut off when a backward current is generated inaccordance with the configuration of the relay disclosed in JapanesePatent No. 3321963, the arc occurring between the contacts will bedistorted towards a region between the two contact pairs by the Lorentzforce of the magnet. In this case, each arc will be extended towards anadjacent pair of contacts to be linked together, giving rise to theproblem that immediate cutoff cannot be achieved.

Furthermore, superior welding resistance and temperature characteristicare required since the generated heat is great due to the high contactresistance of the contact unit.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a direct current relaythat can cut off a high direct current voltage in a short time even inthe case of backward current while minimizing the number of magnets andallowing down-sizing with a simple configuration.

The present invention is configured including a plurality of contactpairs and a plurality of magnets, wherein each of the plurality ofcontact pairs includes contacts having contact regions. The contacts arearranged allowing opening and closure with respect to each other. Theplurality of contact pairs are arranged such that a plurality of magnetsare aligned on one straight line, and a contact pair is located betweenthe magnets on a line identical to the straight line. Each of theplurality of magnets is provided such that the arc generated between thecontacts at the time of relay cutoff is distorted in a directioncrossing the straight line. Thus, the above object of extinguishing anarc in a short time even on the occasion of backward current can beachieved.

Namely, the present invention includes a plurality of pairs of contacts,wherein the contacts in each pair open/close with respect to each other,and at least one thereof is a movable contact. The contact pairs aredisposed between these magnets such that the plurality of magnets arealigned on one straight line, and the contact pairs are aligned on thesame line. The magnets are arranged so that the counter magnetic polefaces correspond to different magnetic poles. By such arrangement ofmagnets, the arc generated between contacts on the occasion of relaycutoff can be distorted in a direction crossing the straight line.

In the direct current relay of the present invention, two or more pairsof contacts can be provided. For example, when two pairs of contacts areprovided so that they can be connected in series, the contacts of thepairs at one side of the switching direction are identified as an inputcontact and an output contact, whereas the contact of the pairs at theother side of the switching direction is identified as a linking contactconnecting the input contact and the output contact in series on theoccasion of conduction.

Each of the input and output contacts has a contact region. An externalterminal is connected to each of these contacts. The linking contact canbe formed in the shape of a capital U, one of a pair of square brackets(a hollow rectangle with one side open), or a flat plate, for example.When the linking contact is formed in the shape of a capital U or asquare bracket, the protruding sides are identified as the contactregion brought into contact with the input contact or output contact.When the linking contact is formed in the shape of a flat plate, theflat face of the flat plate will be brought into contact with the inputcontact and the output contact.

In this case, the contact region of the input contact and one contactregion of the linking contact constitute one pair of contacts, whereasthe contact region of the output contact and the other contact region ofthe linking contact constitute the other pair of contacts.

By connecting the input contact and the output contact through thelinking contact on the occasion of forming contact (conducting state),the input contact, the linking contact and the output contact will beconnected in series during conduction.

At least two magnets are disposed on a line connecting the input contactand the output contact, so as to sandwich the input contact and theoutput contact. These magnets are arranged so that the counter magneticpole faces correspond to different magnetic poles.

In the case where the contact pairs are disposed so that they can beconnected in series, the current flowing out from the input contact iscarried up to the output contact via the linking contact when respectivecontacts are brought into contact. When respective contacts aredisconnected, all the contacts attain a non-contact state, whereby anarc will be generated between counter contacts. However, the breakingvoltage is divided since respective contacts are connected in series,allowing the arc to be extinguished.

When breaking the contact in the present invention, the arc generatedbetween contacts is blown by the magnetic field of the magnet so as tobe distorted in a direction crossing the straight line. When respectivecontacts are arranged as shown in FIG. 1, for example, so that they canbe connected in series, the current flows as indicated in FIG. 1. Theline of magnetic force is generated always towards the same direction.As a result, based on Fleming's left-hand rule, the arc is distorted bythe Lorentz force so as to extend in a direction orthogonal to the lineconnecting the contact pair and magnet, as shown in FIG. 2.

In the direct current relay of the present invention, each of thecontact pairs may be configured so as to be connected in series, or inparallel.

When the contact pairs are arranged so that they can be connected inseries in the present invention, the contact preferably includes aninput contact, an output contact, at least one intermediate contact withtwo contact regions arranged between the input contact and the outputcontact, and a plurality of linking contacts sequentially connecting inseries the input contact, the intermediate contact, and the outputcontact in a conducting state.

In this context, by disposing the input contact, output contact and theintermediate contact at one side of the switching direction of thecontacts, and disposing the linking contact at the other side of theswitching direction of the contacts, respective contacts can beconnected in series through, for example, the linear opening/closingoperation of the linking contacts.

The input contact, output contact and intermediate contact may bestationary contacts or movable contacts. When the input contact, outputcontact and intermediate contact are movable contacts, the linkingcontact may be a stationary contact. An external terminal is connectedto each of the input contact and the output contact.

The two contact regions of the intermediate contact are brought intocontact with respective different linking contacts. The intermediatecontact can be formed in the shape of, for example, a capital U, asquare bracket (a hollow rectangle with one side open), or a flat plate.When the linking contact is formed in the shape of a capital U or asquare bracket, the ends of respective sides of the U shape or squarebracket are identified as the contact regions. When the linking contactis formed in the shape of a flat plate, the side portions in thelongitudinal direction of the flat plate are identified as contactregions which are brought into contact with the linking contact.

The number of linking contacts is equal to the number of intermediatecontacts plus one. When contact is formed (conductive state), the inputcontact and one contact region of the intermediate contact are connectedthrough one linking contact, and the output contact and the othercontact region of the intermediate contact are connected through anotherone linking contact. When there are a plurality of intermediatecontacts, two linking contacts are employed as the linking contact toconnect the input contact with the intermediate contact, and a linkingcontact to connect the output contact with an intermediate contact.Adjacent contact regions of adjacent intermediate contacts are connectedtogether through another linking contact. By these linking contacts, theinput contact, intermediate contact, and output contact are connected inseries in a conductive state.

A linking contact can be formed in the shape of, for example, a capitalU, a square bracket, or a flat plate. When the linking contact is formedin the shape of a capital U or a square bracket, respective projectingsides are identified as the contact regions of a contact. When thelinking contact is formed in the shape of a flat plate, two contacts ofone side such as an input contact are brought into contact with the faceof the flat plate.

In the case where intermediate contacts are provided in the presentinvention, respective contacts can be connected in series such as in theorder of an input contact, a linking contact, an intermediate contact, alinking contact, and an output contact on the occasion of conduction.

The current flowing out from the input contact when respective contactsmake connection passes through a linking contact, an intermediatecontact, and a linking contact to arrive at the output contact. Whenrespective contacts are disconnected, all the contacts attain anon-contact state to cause occurrence of an arc between countercontacts. However, the breaking voltage is divided since respectivecontacts are connected in series to allow the arc to be extinguished.

Further, it is preferable to dispose all the contacts on the samestraight line also in the case where the present invention is configuredemploying an intermediate contact. Specifically, as shown in FIGS. 7-9,the input contact, intermediate contact, and output contact are disposedon the same straight line, and the plurality of linking contacts aredisposed so as to overlap the input contact, intermediate contact, andoutput contact vertically on the same one line, when viewed in plane.

In the case where the input contact, output contact, and intermediatecontact are disposed at one side of the switching direction of thecontacts, and linking contacts are disposed at the other side of theswitching direction of the contacts, the relay can be cut off by justmoving forward in the switching direction at least the contacts at oneside of the switching direction to achieve switching.

Among a pair of contacts that are to be opened/closed, one may be set asa movable contact and the other may be set as a stationary contact.Alternatively, both may be set as movable contacts to make/break theconnection.

When all the contacts are movable contacts, all the contacts must bedriven simultaneously. Specific means to establish such a timingincludes, for example, those employing timer means. In other words, adrive signal to drive the movable contacts by means of a timer isoutput.

In the case where an intermediate contact is provided, the plurality ofmagnets are disposed on one straight line, and the pair of contacts isdisposed between these magnets on the same line. The magnets distort thearc generated between the contacts on the occasion of the relay cutoffin a direction crossing the straight line. Although an arc will begenerated between contacts at the time of cutoff, the arc can beextinguished in a short time by extending the arc outwards through theLorentz force of the magnet.

In the present invention, the contact area of the contact regionpreferably takes a configuration in which the length in the direction ofthe straight line is shorter than the length in the direction orthogonalto the straight line.

For example, when the aforementioned two pairs of contacts are provided,the input contact and the output contact are disposed on the one samestraight line, and linking contacts are disposed so as to overlap theinput contact and the output contact vertically. When viewed in plane,respective contacts are set on the same one line.

In this context, a contact region is formed at each contact to bebrought into contact with another contact, and the contact area of thecontact region is configured such that the length in the direction ofthe straight line that connects respective contacts is shorter than thelength in the direction orthogonal to the straight line.

A configuration of a contact area of the contact region in which thelength in the direction of the straight line is shorter than the lengthin the direction orthogonal to the straight line includes an oblongshape such as an oval, an ellipse, a rectangle, or the like with thedirection of the minor axis of the contact area corresponding to thedirection of the straight line.

When the plurality of contact pairs are disposed on the same line, thereis a possibility of the entire relay becoming larger in the direction ofthe straight line as the number of contacts increases. It is to be notedthat many direct current relays employ a solenoid to drive the movablecontact. Since the size of this solenoid is determined when acommercially-available product is employed, it is preferable that thecontact does not protrude from the cross sectional area of the solenoid.

Various driving sources can be employed for the opening/closingoperation of the contact. A motor can be employed for the driving sourceof the rotational system. A solenoid or cylinder can be employed for thedriving source of the direct-acting system. When a rotational systemdriving source is employed, the contact is driven via a convertingmechanism to convert a rotational motion into a reciprocating motion.When a direct-acting system driving source is employed, the contact isdriven with the direct-acting system driving source linked to thecontact.

In the case of a configuration in which the contacts are arranged sothat they can be connected in series and an intermediate contact isprovided, it is preferable to form a contact region in each contact thatis to be brought into contact with another contact, and form the contactarea of the contact region to have a length in the contact alignmentdirection shorter than the length in the direction orthogonal to thealignment direction.

The contact region of the stationary contact and movable contact ispreferably formed of Ag (silver) alloy of a chemical compositionincluding 1-9 mass % of Sn (tin) and 1-9 mass % of In (indium), andincludes a first layer identified as the surface region and a secondlayer identified as the inner region. Preferably, the first and secondlayers have the micro Vickers hardness of at least 190 and not more than130, respectively, and the thickness of the first layer is within therange of 10-360 μm.

The reason why the amount of Sn is set to 1-9 mass % is that the weldingresistance of the contact will be degraded if the amount is less than 1mass % and the temperature characteristic of the contact will bedegraded if the amount exceeds 9 mass %. Preferably, the amount of Sn is2-7 mass %.

As used herein, welding resistance refers to the low vulnerability towelding where the contact cannot be cut, particularly the state of thecontact taking hold and not being able to be detached. Temperaturecharacteristic refers to the degree of temperature increase of thecontact in a conductive state. Favorable temperature characteristicimplies that the temperature of the contact does not easily rise on theoccasion of conduction, with less thermal effect on the cable andequipment connected to the relay.

The reason why the amount of In is set to 1-9 mass % is that thetemperature characteristic of the contact is degraded when the amount isoutside this range. When the amount exceeds 9 mass %, the weldingresistance is degraded depending upon the amount of Sn. Preferably, theamount of In is 3-7 mass %.

The reason why the hardness of first layer (generally, 5 g weight load)is set to at least 190 in micro Vickers hardness is that the weldingresistance and temperature characteristics will be degraded when thehardness is below this level. Furthermore, the reason why the hardnessof the second layer is set to not more than 130 in micro Vickershardness is that the contact will become brittle and the weldingresistance is degraded if the hardness exceeds this level.

It is desirable that the first layer has a hardness of at least 240 andthe second layer has a hardness of not more than 120. In the presentinvention, the hardness is confirmed with micro Vickers hardness at anarbitrary site in respective regions of the first layer and the secondlayer on a cross section perpendicular to the surface of the contact.The contact of the present invention may have a hardness distribution ineach of the first and second layers.

There is a drop in hardness (at least 60 in micro Vickers hardness) atthe boundary between the first layer and the second layer. This boundaryincludes a region (referred to as intermediate region hereinafter)having a hardness intermediate the hardness of the two layers (i.e. thehardness is within a range that is lower than the lower limit of thehardness of the first layer and that exceeds the upper limit of thehardness of the second layer).

The first layer has a thickness of 10-360 μm. If the thickness is lessthan the lower limit, the welding resistance and temperaturecharacteristic will be degraded. If the thickness exceeds the upperlimit, the temperature characteristic of the contact is degraded.Preferably, the thickness is 30-120 μm. The contact having a first layerand second layer may include those with an intermediate region. It isdesirable that the thickness of the intermediate region is not more than200 μm. If the thickness thereof exceeds 200 μm, the temperaturecharacteristic of the contact is easily degraded. Preferably, thethickness is equal to or less than 100 μm.

In addition to the above-described basic component, the contact mayinclude, as a subcomponent, at least one element selected from the groupconsisting of Sb (antimony), Ca (calcium), Bi (bismuth), Ni (nickel), Co(cobalt), Zn (zinc) and Pb (lead). Generally, most of these componentsare dispersed in the form of a compound, particularly an oxide, in theAg matrix.

It is to be noted that the desirable dispersion range differs dependingupon each component. For example, the ranges are 0.05-2 (Sb), 0.03-0.3(Ca), 0.01-1 (Bi), 0.02-1.5 (Ni), 0.02-0.5 (Co), 0.02-8.5 (Zn), and0.05-5 (Pb) in element-converted mass % unit. The element in theparenthesis refers to the subject element. If the amount falls outsidethe range set forth above for each of the foregoing components, thetemperature characteristic may be degraded depending upon the type ofthe direct current relay. Particularly, excess of the upper limit mayalso cause degradation in the welding resistance, depending upon thetype of the relay.

In general, the subcomponents set forth above affect somewhat of thecontact performance. Other components thereof are cited in thefollowing. A slight amount of any thereof may be included within therange according to the object of the present invention. The desirablecontaining amount differs depending upon the component. The values inthe parenthesis corresponding to a symbol of element is represented inelement-converted mass % unit whereas those corresponding to a molecularformula is the tolerable upper limit represented in the relevantmolecule-converted mass % unit. Ce (5), Li (5), Cr (5), Sr (5), Ti (5),Te (5), Mn (5), AlF₃ (5), CrF₃ (5) and CaF₂ (5), Ge (3) and Ga (3), Si(0.5), Fe (0.1) and Mg (0.1).

As the method to form a contact having a first layer and a second layer,the molten casting method, powder metallurgy, and the like can be cited.

For example, the molten casting method includes the procedures set forthbelow. First, ingots subjected to molten casting so as to correspond torespective chemical compositions for the first and second layers areprepared. These ingots are rolled roughly, and the two rolling membersare hot-pressed. At that stage, or a later stage, a thin connectionlayer such as of pure Ag set forth above, if necessary, is attached bycompression.

Further rolling is applied to form a sheet of a predetermined thickness.Punching, or further forming is applied to achieve a Ag alloy materialof a size approximating the final configuration. Then, the material issubjected to internal oxidation (post-oxidation) such that the metalcomponents of Sn, In and the like are converted into oxides.

Prior to the molten casting method, a compound other than the oxides ofthe constituent elements can be included. Additionally, a thermaltreatment or a step of adjusting the configuration, and the like can beapplied appropriately, subsequent to the rolling step, as necessary. Inthis case, the fine structure of each layer can be controlledintentionally to alter the material property, the level thereof, and thelike by devising the thermal treatment condition.

When the contact region is to be produced by powder metallurgy, twopredetermined compositions of powder such as Sn and In, and powder ofAg, for example, are blended and mixed, followed by thermal treatmentfor internal oxidation (pre-oxidation). The obtained two types of powderare layered and filled in a mold to be subjected to compression molding,resulting in a preform. The powder of Sn, In and the like and the powderof Ag may be mixed together with another compound.

Various types of deformation processes such as hot extrusion, hot/coldrolling, hot forging and the like can be applied to the preform. Athermal treatment and/or a step to adjust the configuration are added,as necessary, subsequent to the rolling step, likewise the castingmethod set forth above. Each layer can have its property controlled to adesired level by devising the thermal treatment condition.

After the material of the second layer alone is prepared by theprocedure conforming to the aforementioned molten casting method orpowder metallurgy, the first layer can be formed by various means suchas thick film formation through thermal spraying, CVD (Chemical VaporDeposition) and the like, thick film printing through screen printingand the like, coating followed by baking, and the like. Bonding of thealloy sheet constituting the first layer and the alloy sheetconstituting the second layer can be effected by various means such asdiffusion joining through hot isostatic pressing, hot extrusion and thelike. Furthermore, by applying thermal treatment, the fine structure ofeach layer can be controlled intentionally to achieve a desiredproperty.

In the relay of the present invention, the Ag alloy material forming thecontact is within the range of the conditions set forth above, andinclude those having the same chemical composition for the first layerand the second layer. When the first and second layers have the samechemical composition, the hardness of respective layers are setdifferent by means set forth afterwards.

For example, the first layer alone is rapidly heated and rapidly cooledso that the residual stress of the first layer is greater than that ofthe second layer. Alternatively, the method including the step ofapplying shot blasting to the first layer at the surface for hardeningcan be employed.

There is also the method of applying hot rolling or cold rolling andthen a thermal treatment to the Ag alloy sheet, i.e. applying theso-called thermo mechanical processing (heat process), followed byinternal oxidation to precipitate needle-like oxide particles smallerthan those of the second layer at the first layer to increase thehardness at the surface. There is also the method of altering theforging ratio between the first and second layers when the Ag alloysheets of the first and second layers are subjected to rolling and hotpressing.

Further, the material of the contact region is within the range of theconditions set forth above, and also includes those whose amount of Snin the first layer is equal to or greater than that in the second layer.This ensures that the hardness of the first layer is higher than that ofthe second layer.

In the formation step of the contact region by molten casting, powdermetallurgy and the like, the first and second layers are preferablysubjected to internal oxidation. The internal oxidation includespost-oxidation and pre-oxidation.

Post-oxidation is known as the method of conducting internal oxidationafter finishing or nearly finishing in the final contact configurationin the alloy form.

Pre-oxidation is known as the method of subjecting the powder orparticles of the alloy to internal oxidation, followed by molding,compression and sintering the same.

Since the arc generated between contacts of a contact pair on theoccasion of cut off is distorted in a direction crossing a straight linealong which magnets and contact pairs are aligned, the relay can be cutoff in a short time by the voltage cutoff of multi-contacts through theplurality of contact pairs and blow out of an arc by the magnet.

In accordance with the present invention, by dividing the breakingvoltage and blowing away the arc through the magnet, the arc voltage israised in a short time to allow the relay to be cut off in a short time.

Since the arc energy is consumed with the extension of arc through themagnet while cutting off the voltage by the multi-contact, it is nolonger necessary to ensure a predetermined amount of arc extensionrequired for voltage cutoff as in the conventional case. Furthermore,the magnetic force of the magnet to be used can be lowered as comparedto the conventional case, allowing down-sizing of the magnet.

Since the arc extension direction corresponds to a direction crossingthe straight line that connects the contact pairs (the directioncrossing the straight line corresponding to the contact aligneddirection), arcs will not be linked with each other even if a backwardcurrent such as regenerative energy is generated. A backward current canbe accommodated sufficiently.

Since a pair of contact is provided between a plurality of magnets, itis no longer necessary to provide a pair of magnets for each contactpair. The number of magnets used can be reduced as compared to those ofa conventional relay (Japanese Patent No. 3321963). Therefore, the costcan be reduced.

Furthermore, in the case where the contact area of the contact region isformed such that the length in the contact aligning direction (thestraight line direction) is shorter than the length in the directionorthogonal to the straight line direction, increase of the length insaid direction of the straight line, i.e. the contact aligning directionof the relay, can be suppressed to the minimum level while ensuringsufficient contact area of the contact. Therefore, the relay can bereduced in size.

When a solenoid is to be employed with the plurality of contact pairsaligned in one row, effective space is achieved in the area of the crosssection of the solenoid in the direction orthogonal to the straight linedirection. By extending the contact area towards the effective space andreducing the length in the aligning direction, the volume of the entirerelay can be reduced.

Further, in the case where a solenoid, for example, is employed in therelay, effective space as set forth above is achieved in the directionorthogonal to the straight line direction. Since this effective spacecan be employed as the space for extending the arc, it is no longernecessary to provide extra space for the arc.

In the case where a configuration is employed in which respectivecontacts are arranged so that they can be connected in series, and anintermediate contact and a plurality of linking contacts are provided,increase of the length in the contact aligning direction can besuppressed to the minimum while ensuring sufficient contact area of thecontact even if the number of contact pairs increases by disposing allthe contacts on the same one line and forming the contact area of thecontact region in the shape as set forth before.

In the case where contact pairs are arranged so that they can beconnected in series in a conducting state, division of the voltagebetween the contacts on a cutoff occasion allows the voltage to be cutoff in a shorter time. As a result, damage of the contact through thearc current can be suppressed by reducing the voltage across thecontacts.

By increasing the number of contacts and connecting these contacts inseries, a hermetic structure of sealing the extinction gas is no longerrequired. Therefore, a direct current relay can be fabricatedeconomically.

In the case where the contact pairs are arranged so that they can beconnected in in parallel in a conducting state, the current can bedivided. By reducing the current flowing across one contact, damage ofthe contact caused by arc current can be suppressed.

Furthermore, by forming the contact region of the contact with amaterial superior in welding resistance, the contact will not be weldedeven if a large current flows during short-circuiting of the relay.Thus, cutoff can be achieved reliably.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a direct current relay with contacts thatcan be connected in series according to a first embodiment of thepresent invention, corresponding to a conductive state where contact isestablished.

FIG. 2 is a schematic view of a direct current relay with contacts thatcan be connected in series according to the first embodiment of thepresent invention, corresponding to a cutoff state where contact is notestablished.

FIG. 3 is a longitudinal sectional view showing a schematic structure ofthe direct current relay of the present invention in accordance with thefirst embodiment.

FIG. 4 is a transverse sectional view showing a schematic structure ofthe direct current relay of the present invention in accordance with thefirst embodiment.

FIG. 5 is a schematic view of a direct current relay with contacts thatcan be connected in parallel according to a second embodiment of thepresent invention, corresponding to a conductive state where contact isestablished.

FIG. 6 is a schematic view of the direct current relay with contactsthat can be connected in parallel according to the second embodiment ofthe present invention, corresponding to a cutoff state where contact isnot established.

FIG. 7 is a schematic view of a direct current relay with many contactsthat can be connected in series according to a third embodiment of thepresent invention, corresponding to a conductive state where contact isestablished.

FIG. 8 is a schematic view of the direct current relay with manycontacts that can be connected in series according to the thirdembodiment of the present invention, corresponding to a cutoff statewhere contact is not established.

FIG. 9 a longitudinal sectional view showing a specific structure of thedirect current relay of the present invention in accordance with thethird embodiment.

FIG. 10 is a sectional view of the direct current relay of the presentinvention in accordance with the third embodiment taken along line X-Xof FIG. 9.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described hereinafter.

First Embodiment

A direct current relay according to a first embodiment includes in acasing 1, as shown in FIG. 3, an input contact 21 and an output contact22 that are stationary contacts, a linking contact 31 that is a movablecontact, and a contact driving mechanism 4.

Input and output contacts 21 and 22 include contact regions 21 a and 22a to be brought into contact with linking contact 31, and terminalconnections 21 b and 22 b, respectively. An external terminal isconnected to each of terminal connections 21 b and 22 b.

Linking contact 31 is U-shaped in cross section. The flat face at bothsides of this U shape is identified as a contact region 31 a. Contactregion 31 a of linking contact 31 is brought into contact with contactregion 21 a of input contact 21 and contact region 22 a of outputcontact 22.

In the present embodiment, contact region 21 a of input contact 21 andone contact region 31 a of linking contact 31 constitute one contactpair, whereas contact region 22 a of output contact 22 and the othercontact region 31 a of linking contact 31 constitute another contactpair.

Each contact region of input contact 21, linking contact 31 and outputcontact 22 is formed of Ag alloy of a chemical composition including 1-9mass % of Sn and 1-9 mass % of In. The contact region includes a firstlayer corresponding to the surface region and a second layercorresponding to the inner region. The first layer and the second layerhave a micro Vickers hardness of at least 190 and not more than 130,respectively. The thickness of the first layer is within the range of10-360 μm. Each contact region is subjected to internal oxidation bypost-oxidation in the form of a chip. The internal oxidation is effectedby maintaining the chip for 170 hours at 750° C. in an oxygen ambient of4 atmospheres (405.3 kPa).

Input contact 21, linking contact 31 and output contact 22 are disposedso as to be located on one same straight line. Specifically, arrangementis established such that, when one contact region 31 a of linkingcontact 31 is brought into contact with contact region 21 a of inputcontact 21 and the other contact region 31 a of linking contact 31 isbrought into contact with contact region 22 a of output contact 22, thecontact pairs of such connecting state are aligned on the same straightline.

By disposing respective contacts as set forth above and bringing thecontact region of each contact into contact, respective contacts areconnected in series from input contact 21 to output contact 22 vialinking contact 31.

Contact region 21 a of input contact 21 and contact region 22 a ofoutput contact 22 have an oblong face at the area that is to formcontact with the contact region of linking contact 31. Each of contactregions 21 a and 22 a is provided such that the minor axis direction ofthe oblong face of the contact area corresponds to the aligningdirection of respective contacts (said straight line direction). A metalcylindrical block having an oblong contact area for contact regions 21 aand 22 a is employed as input contact 21 and output contact 22.

As shown in FIG. 3, linking contact 31 achieves a reciprocating motionin the contact switching direction by contact driving mechanism 4. Byswitching the contact through contact driving mechanism 4, linkingcontact 31 attains a contacting or non-contacting state with respect toinput contact 21 and output contact 22.

Contact driving mechanism 4 will be described specifically hereinafter.Contact driving mechanism 4 includes a spring 45, and a solenoid 46.Spring 45 is arranged between linking contact 31 and a shaft activateunit 48 of solenoid 46. A driving shaft 47 of solenoid 46 is passedthrough spring 45. Spring 45 urges linking contact 31 in a directionaway from input contact 21 and output contact 22, i.e. in the contactopening direction.

Solenoid 46 serves to cause linking contact 31 to reciprocate in thecontact switching direction, and includes a driving shaft 47 having oneend fixed to linking contact 31, and a shaft activate unit 48 to causedriving shaft 47 to reciprocate in the contact switching direction.Driving shaft 47 has one end side fixed at an intermediate site oflinking contact 31, and the other end side inserted in a hole (notshown) formed in shaft activate unit 48.

When in an ON state where current flows, where shaft activate unit 48moves driving shaft 47 in a direction exiting from the hole (contactopening direction). Specifically, when shaft active state 48 is ON,driving shaft 47 is moved against the spring force of spring 45 in adirection causing linking contact 31 to form contact with input contact21 and output contact 22 (contact closing direction).

When shaft activate unit 48 is OFF, the extended spring 45 is restoredto its original status, and driving shaft 47 moves through the springforce of spring 45 in a direction away from input contact 21 and outputcontact 22 (contact opening direction).

Linking contact 31 reciprocates in accordance with the movement ofdriving shaft 47 of solenoid 46. When linking contact 31 moves in acontact closing direction, contact regions 31 a of linking contact 31are brought into contact with contact regions 21 a and 22 a of inputcontact 21 and output contact 22, simultaneously.

When linking contact 31 moves in the contact opening direction, contactregions 31 a of linking contact 31 are drawn away from contact regions21 a and 22 a of input contact 21 and output contact 22, simultaneously.As such, linking contact 31 is driven to open/close with respect toinput contact 21 and output contact 22 through contact driving mechanism4.

A direct current power supply is connected to terminal connection 21 bof input contact 21 via a terminal (not shown), wherebyconduction/cutoff is effected by establishing connection ordisconnection of respective contacts.

In the present embodiment, the direct current relay includes threesheet-like permanent magnets 5 in casing 1. Permanent magnets 5 arelocated between input contact 21 and output contact 22, and atrespective outer sides of input contact 21 and output contact 22.

Further, permanent magnets 5 are aligned on one straight line identicalto the line where contact pairs are aligned, as shown in FIGS. 1 and 2,such that one pole (for example, N pole) is located at the same side. Bythese permanent magnets 5, a magnetic field is to be applied betweencontact region 21 a of input contact 21 and one contact region 31 a oflinking contact 31, and between contact region 22 a of output contact 22and the other contact region 31 a of linking contact 31. The magneticfield of permanent magnet 5 causes an arc 100 that is generated betweenrespective contacts on the occasion of contact cutoff to be extended anddistorted by the Lorentz force.

In a contact conducting mode of the present invention, current flowsfrom input contact 21 to flow in series to output contact 22 via linkingcontact 31. In the state shown in FIG. 2, permanent magnets 5 aredisposed such that the line of magnetic force flows from left to right.Therefore, based on Fleming's left hand rule, the Lorentz force inducesalternately a frontward force and a backward force in FIG. 2, wherebyarc 100 generated at the time of contact cutoff is distorted frontwardsand backwards alternately.

Contact conduction and cut off will be described here. When conductionis to be established by closing the contacts, respective contacts attainthe conducting state by closing linking contact 31 to bring linkingcontact 31 into contact with input contact 21 and output contact 22(state of FIG. 1).

When connection is to be opened across the contacts to achieve cutoff,the opening operation of linking contact 31 causes disconnection oflinking contact 31 from input contact 21 and output contact 22 toachieve cutoff (state of FIG. 2).

On the occasion of cutoff, arc 100 generated between respective contactsis distorted in the direction set forth above by the magnetic field ofpermanent magnets 5.

The connection of two pairs of contacts in series in the presentembodiment is advantageous in that an arc 100 can be extinguished withthe breaking voltage being divided and with arc 100 extended by themagnetic field. Therefore, the voltage can be cut off in a short time.Furthermore, an extremely compact direct current relay can be realized.Since respective contacts are arranged in series for division of thebreaking voltage, the durability of the contacts can be improved.

The extending direction of the arc differs alternately along the aligneddirection of contacts and magnets. Therefore, arcs will no longer belinked together even if a backward current such as of regenerativeenergy is generated. Backward current can be accommodated sufficiently.

In the direct current relay of the first embodiment, the contact regionof each contact is formed of a material superior in welding resistance.Therefore, the contact will not be welded and can be disconnected evenif a large current flows during short-circulting.

Second Embodiment

In the first embodiment, a direct current relay that can have contactpairs connected in series in a conducting state was described. Thesecond embodiment is directed to allowing contact pairs to be connectedin parallel in a conducting state.

As shown in FIGS. 5 and 6, the direct current relay according to thesecond embodiment includes an input contact 6 identified as a fixedcontact, and an output contact 7 identified as a movable contact. Bothinput contact 6 and output contact 7 have an approximately U shape incross section. The flat face at both sides of this U shape areidentified as contact regions 61 and 71. Each of these contacts includestwo contact regions 61 and 71. The two contact regions 61 of inputcontact 6 are brought into contact with two contact regions 71,respectively, of counter output contact 7.

In the present embodiment, one contact region 61 of input contact 6 andone contact region 71 of output contact 7 constitute one contact pair.The other contact region 61 of input contact 6 and the other contactregion 71 of output contact 7 constitute another contact pair.

Input contact 6 and output contact 7 are disposed so that respectivecontact regions 61 and 71 are located on one same straight line in aconnecting state. By such arrangement of respective contacts andestablishing contact of respective contact regions of each contact, asshown in FIG. 5, respective contact pairs are connected in parallel frominput contact 6 to output contact 7.

In the present embodiment, respective contact regions 61 and 71 of inputcontact 6 and output contact 7 are formed of Ag alloy of the chemicalcomposition including 1-9 mass % of Sn and 1-9 mass % of In. The contactregion includes a first layer corresponding to the surface region and asecond layer corresponding to the inner region. The first layer and thesecond layer have a micro Vickers hardness of at least 190 and not morethan 130, respectively. The thickness of the first layer is within therange of 10-360 μm. Each contact region is subjected to internaloxidation by post-oxidation in the form of a chip. The internaloxidation is effected, for example, by maintaining the chip for 170hours at 750° C. in an oxygen ambient of 4 atmospheres (405.3 kPa).

The contact area of each contact region 61 of input contact 6 has anoblong face in the second embodiment. Each of contact regions 61 isprovided such that the minor axis direction of the oblong face of thecontact area corresponds to the aligning direction of respectivecontacts (said straight line direction).

Likewise in the present embodiment, three permanent magnets 5 areprovided between contact regions 61 of input contact 6, and atrespective outer sides of two contact regions 61. Permanent magnets 5are aligned on one straight line, as shown in FIGS. 5 and 6, such thatone pole (for example, N pole) is located at the same side. By thesepermanent magnets 5, a magnetic field is to be applied between contactregion 61 of input contact 6 and contact region 71 of output contact 7.The magnetic field of permanent magnet 5 causes an arc 100 that isgenerated between respective contacts on the occasion of contact cutoffto be extended and distorted by the Lorentz force.

In a contact conducting mode of the present embodiment, current flowsfrom input contact 6 to flow in parallel to output contact 7 via the twocontact regions. In the state shown in FIG. 6, permanent magnets 5 aredisposed such that the line of magnetic force flows from left to right.Therefore, based on Fleming's left hand rule, the Lorentz force inducesa frontward force in FIG. 6, whereby arc 100 generated at the time ofcontact cutoff is entirely distorted frontwards.

Even in the case where respective contact pairs are disposed to allowconnection in parallel, arcs will not interfere with each other duringconduction, and arc interference is suppressed even when a backwardcurrent flows.

The direct current relay of the second embodiment has the contact regionof each contact formed of a material superior in welding resistance.Therefore, the contact can be disconnected without the contacts beingwelded even if a large current flows during short-circuiting.

Third Embodiment

As shown in FIG. 9, a direct current relay according to a thirdembodiment includes, in casing 1, a plurality of stationary contacts 2,a plurality of movable contacts 3, and a contact driving mechanism 4.

Stationary contact 2 includes, as shown in FIG. 9, an input contact 21to which an external terminal is connected, an output contact 22, andone intermediate contact 23 disposed between contacts 21 and 22.

Input contact 21 and output contact 22 include respective one of contactregions 21 a and 22 a to be brought into contact with movable contact 3,and terminal connections 21 b and 22 b, respectively. Terminalconnections 21 b and 22 b protrude from casing 1.

Intermediate contact 23 has a U shape or a square bracket shape in crosssection. A contact region 23 a to be brought into contact with movablecontact 3 is formed at each end side of the U shape. Although not shown,input contact 21, output contact 22 and intermediate contact 23 aresecured in casing 1 by a screw and the like.

Movable contact 3 includes two linking contacts 31 that is brought intocontact with contact region 21 a of input contact 21 of stationarycontact 2 and one contact region 23 a of intermediate contact 23, andwith contact region 22 a of output contact 22 and one contact region 23a of intermediate contact 23.

Linking contact 31 includes a support unit 31 b with a flat region, andtwo contact regions 31 a. Contact region 31 a is fixed to the flatregion of support unit 31 b to establish contact with any of contactregion 21 a of input contact 21, contact region 22 a of output contact22, and contact region 23 a of intermediate contact 23.

Arrangement is established in casing 1 such that input contact 21,intermediate contact 23, output contact 22, and linking contact 31 arelocated on one same straight line. Specifically, in a state wherestationary contact 2 and movable contact 3 overlap, respective contactsare disposed so as to be located on one same line when viewed from thenon-contacting face of one contact.

By such arrangement of contacts, establishing connection of the contactregion of respective contacts leads to the connection of respectivecontacts in series, from input contact 21 to output contact 22 via onelinking contact 31, intermediate contact 23, and the other linkingcontact 31.

Contact region 21 a of input contact 21, contact region 22 a of outputcontact 22, contact region 23 a of intermediate contact 23, and contactregion 31 a of linking contact 31 are formed of Ag alloy of the chemicalcomposition including 1-9 mass % of Sn and 1-9 mass % of In. The contactregion includes a first layer identified as the surface region and thesecond layer identified as the inner region. The contact region isformed of a material wherein the first and second layers have a microVickers hardness of at least 190 and not more than 130, respectively,and the thickness of the first layer is within the range of 10-360 μm.Each contact region is subjected to internal oxidation by post-oxidationin the form of a chip. The internal oxidation is effected by maintainingthe chip for 170 hours at 750° C. in an oxygen ambient of 4 atmospheres(405.3 kPa).

Contact region 21 a of input unit 21, contact region 22 a of outputcontact 22, contact region 23 a of intermediate contact 23 and contactregion 31 a of linking contact 31 are formed so that the contacting areathat is to be brought into contact with the other contact region has anoblong face (for example, refer to FIG. 10 for contact region 31 a oflinking contact 31). Each contact region is disposed so that thedirection of the minor axis of the oblong contact area corresponds tothe aligning direction of respective contacts. A cylindrical metal blockhaving an oblong contact area is employed for each contact region.

Linking contact 31 is set to reciprocate in the contact switchingdirection by contact driving mechanism 4. The contacts are opened/closedby contact driving mechanism 4, and linking contact 31 attains acontacting or non-contacting state with respect to input contact 21,output contact 22 and intermediate contact 23.

Contact driving mechanism 4 will be described specifically hereinafter.Contact driving mechanism 4 includes a contact member 41, two firstsprings 42, one second spring 43, and a solenoid 44.

Support member 41 supports in an insertable manner a support shaft 31 chaving one side end fixed to a support region 31 b of linking contact31. A flange 31 d is provided at the other end side of support shaft 31c.

First spring 42 is disposed between support member 41 and support region31 b. Support shaft 31 c passes through first spring 42. Second spring43 is disposed between support member 41 and casing 1 to bias supportmember 41 in a contact opening direction.

Solenoid 44 serves to cause support member 41 to reciprocate in thecontact switching direction, and includes a driving shaft 44 a havingone end fixed to support member 41, and a shaft activate unit 44 b tocause driving shaft 44 a to reciprocate in the contact switchingdirection. Driving shaft 44 a has one end side fixed at an intermediatesite of support member 41, and the other end side inserted in a hole(not shown) formed in shaft activate unit 44 b.

When in an ON state where current flows, shaft activate unit 44 b movesdriving shaft 44 a in a direction exiting from the hole (contact closingdirection). Specifically, when shaft active state 44 b is ON, drivingshaft 44 a is moved against the spring force of second spring 43 in adirection towards stationary contact 2 (contact closing direction),causing movable contact 3 to form contact with stationary contact 2.When shaft active state 44 b is OFF, driving shaft 44 a is moved awayfrom stationary contact 2 by the spring force of second spring 43(contact opening direction).

Support member 41 reciprocates in accordance with the movement ofdriving shaft 44 a of solenoid 44. When support member 41 moves in thecontact closing direction, support region 31 b of linking contact 31 isurged towards stationary contact 2 via first spring 42 by support member41, whereby contact regions 31 a of two linking contacts 31 are broughtinto contact with contact regions 21 a, 22 a and 23 a of stationarycontact 2 at the same time.

When support member 41 moves in the contact opening direction, supportregion 31 b of linking contact 31 is pulled back by support member 41via flange 31 d of support shaft 31. Contact regions 31 a of the twolinking contacts 31 are drawn away simultaneously from contact regions21 a, 22 a and 23 a of stationary contact 2. By contact drivingmechanism 4, movable contact 3 opens/closes with respect to stationarycontact 2.

A direct current power supply is connected to terminal connection 21 bof input contact 21 via a terminal (not shown). Conducting/cut off iseffected by establishing connection/disconnection of respectivecontacts.

In the present embodiment, the direct current relay includes threesheet-like permanent magnets 5 in casing 1. Permanent magnets 5 aredisposed at two sites of the non intermediate contact side of inputcontact 21 and output contact 22, and at one site between linkingcontacts 31 between two contact regions 23 a of intermediate contact 23.

As shown in FIG. 8, permanent magnets 5 are disposed on one straightline so that one pole (for example, N pole) is always located at thesame side. A magnetic field is applied between stationary contacts 2 andmovable contact 3 by these permanent magnets 5. The magnetic field ofpermanent magnets 5 causes arc 100 that is generated between respectivecontacts during contact cutoff to be extended and distorted by theLorentz force.

In the present embodiment, current flows from input contact 21 in acontact conducting state, whereby current flows in series to outputcontact 22 via linking contact 31, intermediate contact 23, and linkingcontact 31. In the state shown in FIG. 8, permanent magnets 5 aredisposed so that the line of magnetic force flows from left to right. ByFleming's left hand rule, the Lorentz force induces a frontward forceand backward force alternately in FIG. 8, whereby arc 100 generated atthe time of contact cutoff is distorted frontwards and backwardsalternately.

Contact conduction and cutoff will be described here. When a conductingstate is to be achieved by closing the contacts, movable contact 3 isclosed to form contact between movable contact 3 and stationary contact2. Thus, a conducting state is achieved (the state in FIG. 7).

When contacts are to be opened for cutoff, the opening operation ofmovable contact 3 causes detachment between movable contact 3 andstationary contact 2 for cutoff (the state in FIG. 8). Although arc 100is generated between stationary contact 2 and movable contact 3 at thetime of this cutoff, arc 100 is distorted in the direction set forthabove by the magnetic field of permanent magnets 5.

Since a plurality of contacts are connected in series in the presentembodiment, the breaking voltage can be divided to effect arcextinguishing. Therefore, the voltage can be cut off in a short time. Asa result, a hermetic structure around the contact is not required. Sincearc 100 can be extinguished indispensible of great extension, anextremely compact direct current relay can be realized. Furthermore,since respective contacts are disposed in series to divide the breakingvoltage, the durability of the contacts can be improved.

Since the contact region of the contact is formed of a material superiorin welding resistance, the contacts can be cut off reliably with nowelding of the contacts even if a large current flows at the time ofshort-circuiting.

By dividing the breaking voltage through a plurality of contact pairsand blowing away the arc by magnet 5 in the present invention, the arcvoltage can be increased in a further shorter time to allow the relay tobe cut off in a short time.

Since the arc energy is consumed by extending the arc through magnets 5while dividing the voltage, it is not necessary to prepare apredetermined level of arc extension required for voltage cutoffFurthermore, the magnetic force of the magnet used can be reduced thanin the conventional case, so that the magnet can be reduced in size.

When a backward current such as of regenerative energy flows in therelay, the arc will be extended towards a counter contact region,resulting in the problem that the arc will be linked.

However, in the direct current relay of the present embodiment, arc 100extends in a direction crossing the contact aligning direction,alternately different. Therefore, even if a backward current such asregenerative energy is generated, the arc will be extended in adirection crossing the contact aligning direction. Therefore, the arcswill not be linked even when a backward current is generated. Thus, abackward current can be accommodated sufficiently.

When a solenoid, for example, is employed in the relay, an effectivespace set forth before is achieved in a direction orthogonal to thecontact aligning direction. This effective space can be used as thespace for arc extension. Therefore, it is no longer necessary to provideadditional space for arcing.

In the present embodiment, an insulator 11 is provided between inputcontact 21 and intermediate contact 23, and between output contact 22and intermediate contact 23, as shown in FIGS. 9 and 10. Insulator 11 isformed in sheet form at a portion of casing 1. By insulator 11,insulation between adjacent contacts is effected during contactestablishment.

Although one of the contacts is set as a stationary contact in thepresent embodiment, both contacts may be movable contacts.

With regards to the direct current relay of a configuration according tothe above-described first embodiment, direct relays were produced withthe contact region of respective contacts formed of Ag alloy of the twotypes of chemical compositions for the first and second layers indicatedin the “chemical composition” column shown in Table 1. The weldingresistance and temperature characteristic were examined based on theseproduced direct current relays.

As to the Ag alloy, ingots were formed by molten casting the Ag alloyhaving the two chemical compositions for the first and second layers.These ingots were roughly worked. Then, the ingots of the first layerand the second layer were overlaid, and subjected to hot pressing by hotrolling at 850° C. in an argon ambient to produce a composite materialformed of two layers of Ag alloy.

The obtained composite material was preheated under conditions identicalto those of hot pressing. Then, a thin pure Ag sheet was attached to theface of the second layer opposite to the first layer by hot pressingsuch that it has a thickness 1/10 the eventual entire thickness. Coldrolling was further applied to result in a hoop-like material. Thematerial was subjected to punching, whereby a composite contact chip oftwo structures, i.e., a structure 1 having a width, length and thicknessof 6 mm, 8 mm and 2.5 mm, respectively, and a structure 2 having awidth, length, and thickness of 6 mm, 6 mm, and 2 mm, respectively.

The obtained chip was maintained (internal oxidation) for 170 hours at750° C. in an oxygen ambient of 4 atmospheres (405.3 kPa) to be employedas a composite contact specimen. The obtained specimen had a first layerof a thickness as shown in Table 1. The thickness of the Ag layer wasapproximately 1/10 the thickness of each chip.

The aforementioned thickness of the first layer can be confirmed, as setforth below, using the cross section of a specimen perpendicular to thesurface, passing through the center of the contact. First, 5 startingpoints are set evenly spaced with each other in a direction horizontalto the surface on a specimen plane in the proximity of the surface. Thehardness was confirmed at sequentially even intervals from the surfacein a direction perpendicular to the surface (thickness direction) fromrespective points. Five curves of the hardness (line graph) wereproduced.

The crossing point of a horizontal line corresponding to the hardnesslevel of 190 of a certain starting point and the aforementioned curve istaken, and the horizontal distance from the surface to this crossingpoint is set as the thickness of the first layer at that starting point.Similarly, the thickness of the first layer at a relevant starting pointfor all the remaining 4 starting points can be taken to set thearithmetical average value of the five obtained data as the thickness ofthe first layer. The thickness of the second layer can be measured in asimilar manner.

In this context, the crossing point with a horizontal line correspondingto a hardness level of 130 is taken, and the horizontal distance fromthe surface to this crossing point can be set as the thickness of thesecond layer. In the case where an intermediate layer is provided, thehorizontal distance between the crossing point with a horizontal linecorresponding to a hardness level of 190 and the crossing point with ahorizontal line corresponding to a hardness level of 130 can be taken asthe thickness of the intermediate layer at a certain starting point. Inthe present example, the thickness of the first layer was measured bythe procedure set forth above. TABLE 1 Average Hardness ThicknessChemical Structure (mass %) (Hm V) of First Specimen First Layer SecondLayer First Second Layer No. Sn In Misc. Sn In Misc. Layer Layer (μm) *10.8 0.9 — 0.6 0.7 — 170 59 50  2 1.2 1.2 — 1.2 1.2 — 192 65 50  3 2.32.2 — 2.2 2.1 — 195 70 50  4 2.3 9.0 — 2.2 2.1 — 193 79 50  5 9.0 3.1 —2.2 2.1 — 250 125 50  6 3.4 3.4 — 3.2 3.1 — 240 110 50  7 5.0 5.0 — 5.05.0 — 280 112 50  8 7.0 7.0 — 7.0 7.0 — 290 125 50  9 8.0 7.5 — 7.8 7.2— 302 127 50 *10  9.2 9.2 — 9.1 9.1 — 310 134 50 11 1.2 1.2 Sb 1.2 1.2Sb 200 75 50 12 2.3 2.2 Sb 2.2 2.1 Sb 220 69 50 13 2.3 9.0 Sb 2.2 2.1 Sb200 70 50 14 9.0 3.1 Sb 2.2 2.1 Sb 260 128 50 15 3.4 3.4 Ni 3.2 3.1 Ni250 115 50 16 5.0 5.0 Ni 5.0 5.0 Ni 293 115 50 17 9.0 9.0 Bi 9.0 8.9 Bi300 128 50 *18  9.2 9.2 Bi 9.1 9.1 Bi 320 139 50 *19  5.0 5.0 Sb et al.5.0 5.0 Sb et al. 300 116 9 20 5.0 5.0 Sb et al. 5.0 5.0 Sb et al. 287114 11 21 5.0 5.0 Sb et al. 5.0 5.0 Sb et al. 286 110 26 22 5.0 5.0 Sbet al. 5.0 5.0 Sb et al. 286 110 32 23 5.0 5.0 Sb et al. 5.0 5.0 Sb etal. 286 110 70 24 5.0 5.0 Sb et al. 5.0 5.0 Sb et al. 286 110 120 25 5.05.0 Sb et al. 5.0 5.0 Sb et al. 286 110 260 26 5.0 5.0 Sb et al. 5.0 5.0Sb et al. 286 110 350 *27  5.0 5.0 Sb et al. 5.0 5.0 Sb et al. 286 110370 28 5.0 5.0 Sb et al. 5.0 5.0 Sb et al. 282 113 50 29 5.0 5.0 Sb etal. 5.0 5.0 Sb et al. 285 102 50 30 4.0 3.0 Ni et al. 4.0 3.0 Ni et al.270 100 50 *31  4.0 3.0 Ni et al. 4.0 3.0 Ni et al. 170 100 50 *32  4.03.0 Ni et al. 4.0 3.0 Ni et al. 270 132 50 33 7.0 7.0 — 7.0 7.0 — 290125 50 34 7.0 7.0 — 7.0 7.0 — 293 128 50 *35  4.0 7.0 7.0 7.0 136 180 50*36  3.4 3.4 — — 3.1 — 150 68 200

The specimen in the table that has the symbol * assigned to each numberindicates a comparison example. The amount of each of miscellaneouscomponents Sb, Ni and Bi of Specimens 11-18 was 0.2 mass %. The firstand second layers of Specimens 19-27 all have the same chemicalstructure, and the amount of miscellaneous components therein was 0.2for each of Sb, Co, and Zn in mass % unit for both layers.

The miscellaneous components and amount thereof in Specimen 28 was 0.1for Sb, Pb, Ni, Bi, Co, and Zn, and 0.2 for Ca in mass % unit. Themiscellaneous components and amount in Specimen 29 was 0.1 for Sb, Ni,Ca, Bi, Co and Zn, and 0.5 for Pb in mass % unit. The miscellaneouscomponents and amount in Specimens 30-32 were 0.2 in mass % unit for Niand Zn. The remainder of the chemical composition of the first andsecond layers other than the components cited in the table include Agand inevitable impurities.

Specimens 1-10 in Table 1 correspond to a group of specimens having thehardness of each layer controlled by altering the amount of Sn and In.Specimens 11-18 correspond to a group of specimens having the amount ofSn and In altered, and further added with miscellaneous components otherthan the above-cited elements. Specimens 19-27 correspond to a group ofspecimens having the thickness of the first layer altered.

Specimens 28-34 have the same chemical composition for both the firstand second layers. Among these specimens, the hardness of the firstlayer was controlled as set forth below. Specimens 28-33 had the rollingworking cross section area ratio of the first layer set to 150% of thesecond layer, and the material was subjected to annealing for 30 minutesat 450° C. in vacuum during the rolling working process of the firstlayer material. Then, following internal oxidation, shot blasting wasapplied for 3 minutes at the projecting pressure of 3 kgf/cm² (294 kPa)onto the surface of the first layer using alumina beads of #120.

Specimen 34 was produced under conditions similar to those of thespecimen set forth above, provided that the annealing temperature andperiod of time during the rolling working process was 750° C. and 5hours, respectively. Although not indicated in Table 1, Specimens 33 and34 had an intermediate region of 190 μm and 230 μm, respectively, inthickness, formed therein.

Specimen 35 had the oxide amount of Sn and In in the first layer setlower than those of the second layer to achieve a hardness of the firstlayer lower than the hardness of the second layer. The Ag alloy of thefirst and second layers corresponding to chemical compositions cited inTable 1 was subjected to molten casting, hot pressing and rolling, andthen subjected to internal oxidation under conditions identical to thoseset forth above.

Specimen 36 had the Ag alloy of the first and second layers with thechemical structure cited in Table 1 subjected to molten casting. Then,the matching faces of the two layers were worked to have recesses of 1mm in width and 0.5 mm in thickness formed at the pitch of 1 mm in onehorizontal direction. The matching faces were hot-pressed withrespective recesses and projections engaging each other, followed byrolling. Then, the same was subjected to internal oxidation underconditions identical to those set forth above.

The thickness of the first layer having respective hardness of thespecimens produced as described above was confirmed by a procedure setforth in the foregoing. All the results are shown in Table 1. Althoughnot indicated in the table, the thickness of the intermediate region inthe specimens other than Specimens 33 and 34 was all less than 100 μm.

The electrical contact chip of structure 1 and the electrical contactchip of structure 2 were attached by silver soldering to the main bodyof the movable contact shown in FIG. 1 and the main body of thestationary contact shown in FIG. 1, respectively, resulting in a contactregion. Then, the contact region was secured to two types of directcurrent relays, i.e. a first frame of an AC rating of 30 A and a secondframe of an AC rating of 50 A. Five of each type of such direct currentrelays were prepared for every composite contact chip pair of respectivespecimen numbers. Using the entire assembly of each specimen, a ratedcurrent was applied for 100 minutes to confirm the initial temperaturecharacteristic by measuring the temperature during the currentapplication.

Then, under a state of 220V load, cutoff testing was conducted using theassembly of each one at the cutoff current of 1.5 kA for the 30 A frameand a cut off current of 5 kA for the 50 A frame to confirm the weldingresistance.

The temperature characteristic subsequent to the cutoff testing wasconfirmed by applying a rated current for 100 minutes subsequently tomeasure the temperature during this application. Excessive load testingwas carried out using assemblies with their initial temperaturecharacteristic confirmed, repeating opening and closure for 50 times atan interval of 5 seconds with a current five times the same ratedcurrent applied to both the 30 A frame and 50 A frame. Then, thetemperature during application was measured under conditions identicalto those for the above-described initial confirmation. Thus, thetemperature characteristic subsequent to excessive load testing wasconfirmed.

Durability testing was conducted using assemblies having the initialtemperature characteristic confirmed, repeating opening and closure for6,000 times at an interval of 5 seconds with the same rated currentconducted for both the 30 A frame and 50 A frame. Then, by measuring thetemperature during application under conditions identical to those forthe above-described initial confirmation, the temperature characteristicsubsequent to durability testing was confirmed.

The evaluation for this series of testing was set in 5 stages, with theresult of each type of the 30 A and 50 A frame integrated for thetemperature characteristic. With regards to welding resistance,evaluation was based on whether welding occurred or not.

The five stages of evaluation for the temperature characteristic was 5for a temperature increase of 50° C. or less, 4 for a temperatureincrease of more than 50° C. and not more than 60° C., 3 for atemperature increase of more than 60° C. and not more than 70° C., 2 fora temperature increase of more than 70° C. and not more than 80° C., and1 for a temperature increase of 80° C. or above. These evaluations areshown in Table 2 corresponding to the specimen numbers in Table 1. InTable 2, the specimen number with * implies a comparison example. TABLE2 Result of Electric Testing Temperature Temperature InitialCharacteristic Temperature Characteristic Specimen Welding TemperatureAfter Excessive Characteristic After After Cutoff No. ResistanceCharacteristic Load Testing Durability Testing Testing *1 x 5 2 2 1  2 ∘5 3 3 3  3 ∘ 5 4 3 3  4 ∘ 5 3 3 3  5 ∘ 3 3 4 3  6 ∘ 4 4 4 4  7 ∘ 3 4 4 3 8 ∘ 3 4 4 3  9 ∘ 3 3 3 3 *10  ∘ 2 1 2 1 11 ∘ 4 3 3 3 12 ∘ 4 3 4 4 13 ∘4 3 3 3 14 ∘ 3 3 3 3 15 ∘ 4 4 4 4 16 ∘ 3 4 4 3 17 ∘ 3 3 4 3 *18  ∘ 3 2 32 *19  x 3 3 2 3 20 ∘ 4 3 3 3 21 ∘ 4 3 3 4 22 ∘ 4 3 4 4 23 ∘ 4 4 4 4 24∘ 4 4 4 4 25 ∘ 4 4 3 4 26 ∘ 3 4 3 4 *27  x 2 4 3 4 28 ∘ 3 4 4 3 29 ∘ 3 44 3 30 ∘ 4 4 4 4 *31  x 5 2 2 2 *32  x 4 2 4 2 33 ∘ 3 4 4 3 34 ∘ 3 4 3 3*35  x 4 2 2 2 *36  x 5 1 2 1

In view of the foregoing results, the following was identified:

(1) A relay employing the contact of the present invention having the Snand In controlled to be within the range of 1-9 mass % for both thefirst and second layers, having the micro Vickers hardness of the firstand second layers set to at least 190 and not more than 130,respectively, and having the thickness of the first layer controlled tobe within the range of 10-360 μm is within the range of sufficient usageapplicability based on the integrated evaluation set forth above. Incontrast, relays employing a contact departing from the scope of thepresent invention do not achieve the level of usage application based onthe integrated evaluation.

(2) The same applies to the case where a small amount of component suchas Sb and/or Ni is added in addition to Sn and In.

(3) The contact chip of Specimen 1, Specimen 10, Specimen 18, Specimen31, Specimen 32, Specimen 35 and Specimen 36 corresponding tocomparative examples depart from the scope of the present invention inhardness level. Direct current relays incorporating such contact chipsdid not achieve the performance of usage application level on anintegrated basis with the exception of some of the property.

INDUSTRIAL APPLICABILITY

Since the relay of the present invention is compact, limited space canbe used effectively when employed as a relay to turn ON/OFF a highvoltage circuit in an automobile of high voltage (approximately 300V)such as a hybrid vehicle.

1. (canceled)
 2. A direct current relay comprising: a plurality ofcontact pairs, and a plurality of magnets (5), wherein each of saidplurality of contact pairs includes contacts (21, 22, 23, 31) havingcontact regions (21 a, 22 a, 23 a, 31 a), said contacts configured toallow opening and closure with respect to each other, said plurality ofcontact pairs are arranged such that said plurality of magnets (5) arealigned on one straight line, and said contact pair is located betweensaid magnets (5) on a line identical to said straight line, each of saidplurality of magnets (5) is provided so as to distort an arc generatedbetween said contacts (21, 22, 23, 31) on an occasion of relay cutoff ina direction crossing said straight line, a contact area of said contactregion (21 a, 22 a, 23 a, 31 a) has a shape such that a length of thecontact area in a direction of said straight line is shorter than alength in a direction orthogonal to said straight line.
 3. The directcurrent relay according to claim 2, wherein said contact pairs arearranged respectively so that they can be connected in series.
 4. Thedirect current relay according to claim 3, wherein said contact includesan input contact (21), an output contact (22), at least one intermediatecontact (23) disposed between said input contact (21) and said outputcontact (22), and having two contact regions (23 a), and a plurality oflinking contacts (31) connecting in series said input contact (21), saidintermediate contact (23) and said output contact (22) sequentially in aconducting state, said input contact (21), said output contact (22) andsaid intermediate contact (23) being disposed at one side of a switchingdirection of said contact, and said linking contact being disposed atthe other side of the switching direction of said contact.
 5. The directcurrent relay according to claim 2, wherein said contact pairs arearranged respectively so that they can be connected in parallel.
 6. Thedirect current relay according to claim 2, wherein said contact region(21 a, 22 a, 23 a, 31 a) is formed of Ag alloy of a chemical compositionincluding 1-9 mass % of Sn and 1-9 mass % of In, said contact regionincluding a first layer at a surface region and a second layer at aninner region, said first layer having a micro Vickers hardness of atleast 190, and said second layer having a micro Vickers hardness of notmore than 130, and said first layer has a thickness in a range of 10-360μm.